Things You'll Need
Liquid herbicide for lawns
Few things are more frustrating than having your lawn become infiltrated with unwanted grasses. When Bermuda grass begins to grow in a lawn of St. Augustine, it can take over in no time. It's best to deal with the problem as quickly as possible. Fortunately, there are herbicides that you can purchase that will make the job of ridding your lawn of Bermuda grass relatively easy.
Purchase a liquid herbicide product that is specifically designed to kill Bermuda grass without hurting the St. Augustine. Read the back of the package to make sure the grass you want to kill is listed, and it states it won't harm the grass you want to keep.
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Fill a pump-up spray bottle with the amount of herbicide needed, per the instructions on the package. Fill up the remainder of the bottle with water.
Spray your lawn with the herbicide, making sure to not water the lawn for at least a day after the application. The Bermuda grass will start to die in one to two days.
Purchase a weed-and-feed herbicide/fertilizer to put down on your yard, if you want to fertilize it as well as kill the Bermuda grass. Read the back of the package to make sure it states it will kill the targeted grass and won't harm your St. Augustine grass.
Water your grass well before you put down the weed-and-feed to help the product work.
Set your spreader to the correct spreading setting, per the instructions on the package.
Pour your weed-and-feed into the spreader and spread throughout your lawn. You should start to see results in one to two days. Don't water your lawn after you've applied the weed-and-feed for at least one day.
Don't use a weed-and-feed and liquid fertilizer right after each other. If you use a liquid fertilizer and want to fertilize your lawn, use a straight lawn fertilizer without an herbicide in it.
Be careful not to use more weed-and-feed than recommended on the packager or you may kill wanted grass.